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Investigation of electrical and optical properties of ag-in-se based devices

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2010
Kaleli, Murat
Ternary chalcopyrite compound semiconductors have received much attention as the absorbing layers in the polycrystalline thin film solar cell structures. Most widely used one is CuInSe2 and CuInGaSe2 structures, but there are some diffusion problems with copper atoms in the structure. On the other hand, AgInSe2 is promising material with several advantages over the CuInSe2. The aim of this study was to investigate and optimize the production and post-production methods of the Ag-In-Se thin film based heterostructure devices. In this study Ag-In-Se thin films were deposited on glass, ITO coated glass and Si wafer substrates by thermal evaporation and RF/DC sputtering methods. The structural, electrical and optical properties of the devices were investigated. The XRD measurements of the thermally evaporated films showed that as-grown films in amorphous nature. By annealing the films under nitrogen atmosphere, the AIS films turn to polycrystalline structure which including AgIn5Se8 and δ−In2Se3 multi-phases with n-type conductivity. p-Si/n-AIS heterojunctions showed very good diode behavior with 4 order rectification factor. Annealing under nitrogen atmosphere decreased the series resistance of the devices and calculated solar cell conversion efficiency and fill factor of devices increased up to n=2.6% and FF=63, respectively. The XRD measurements of layer-by-layer sputtered AIS films were showed that as-grown films amorphous in nature. The AIS thin films were annealed at 300oC temperature under selenium ambient and mono-phase AgInSe2 with desired p-type conductivity were obtained. n-Si/p-AIS heterojunctions showed very good diode behaviors with 6 order rectification factor. The results of the study showed that AIS thin film has a photoresponce maximum which is exactly matching with solar photon energy maxima. High series resistance of the devices increases the recombination in the junction and this results in the lower solar conversion efficiency. The adequate electrical, optical and structural properties of the AIS thin films reveals that p-AIS thin films could be used as a solar cell absorber layer with an appropriate window layer, such as CdS.